Regarding the development of higher image quality of projectors, there is increasing demand for higher resolution, to say nothing of brightness and color reproducibility. In response, technology has been proposed relating to the higher resolution of a projected image.
For example, Patent Document 1 discloses a projection display device that is capable of providing a projected image having twice the number of pixels as the number of pixels of a display panel.
The projection-type display device described in Patent Document 1 has a liquid crystal panel for display, a projection optical system that enlarges and projects the image formed on the liquid crystal panel for display on a screen, and shifting means provided between the liquid crystal panel for display and the projection optical system.
The shifting means is a component that uses the double-refraction phenomenon of a quartz plate to shift the optical path and includes a quartz plate and a liquid crystal panel for controlling the polarization direction. The image light from the liquid crystal panel for display is irradiated into the quartz plate by way of the liquid crystal panel for controlling the polarization direction.
The liquid crystal panel for controlling polarization direction is provided for controlling the polarization direction of light that is irradiated into the quartz plate. The optical path of light that is emitted from the quartz plate when the liquid crystal panel for controlling the polarization direction is OFF is shifted in a predetermined direction with respect to the optical path of light that is emitted from the quartz plate when the liquid crystal panel for controlling the polarization direction is ON.
An original image having a number of pixels that is twice the number of pixels of the liquid crystal panel for display is divided into two images I1 and I2 at a spacing of one pixel in the horizontal direction, and images I1 and I2 are displayed in time divisions on a liquid crystal panel for display. The liquid crystal panel for polarization control is turned ON during the display interval of image I1 and the liquid crystal panel for polarization control is turned OFF during the display interval of image I2.
The projected image of image I1 and the projected image of image I2 are displayed on the screen in time divisions. The projected image of image I2 is displayed at a position that is shifted by one-half the pixel pitch in the horizontal direction with respect to the projected image of image I1. By making the display cycle of images I1 and I2 shorter than the afterimage interval of the human eye, an image in which the projected images of images I1 and I2 are superposed can be observed. This observed image (the superposed image of images I1 and I2) has a number of pixels that is equivalent to the original image.
Configurations in which an optical path shifting means is provided between a liquid crystal panel and projection lens to increase the number of pixels of a projected image are also disclosed in Patent Documents 2 and 3.